Sixteen percent of Clinton supporters questioned in a CNN/Opinion Research Corporation survey said they are not likely to vote in the general election if Obama is the Democratic nominee.

An equal number of Obama supporters said they'll sit it out come November if Clinton is their party's nominee.

"The problem for the Democratic Party in November may not be crossover votes: Clinton supporters choosing [Sen. John] McCain in the fall if Obama wins the nomination or Obama voters doing likewise if Clinton gets the nod," CNN polling director Keating Holland said. "The real problem may be that those disaffected Clinton or Obama supporters may just stay at home in November, which could cost the party dearly in some key states.

"If the Obama stay-at-home vote is largely African-American, that will affect Democrats' chances on the ballot in several Southern states and could take states like Virginia off the table completely," Holland said. "It might even hurt Democrats in states where the party relies on heavy turnout in large urban areas, such as Pennsylvania and Ohio. Watch how Clinton-Obama squabble could split Democratic party »

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"And if the Clinton stay-at-home vote is predominantly female, that will hurt the party everywhere," he added.

But polls are just snapshots of how people feel at the moment. If the Democrats can come together and agree on a nominee, most of the ill will could be just a memory by November.

Clinton spoke out Thursday in Fayetteville, North Carolina, regarding party unity, and she had a warning to Democrats who may consider sitting out the November election or even voting for McCain, the presumptive GOP nominee.

"Please think through this decision. It is not a wise decision for yourself or your country," Clinton said. "There are, in my view, significant differences between Sen. Obama and myself, but those differences pale to the differences between us and Sen. McCain. I intend to do everything I can to make sure we have a unified Democratic party.

"When this contest is over and we have a nominee, we're going to close ranks, we're going to be united, and I have no doubt about that, because the most important goal is for us to put a Democrat back into the White House next January," Clinton added.

But a look back shows that primary animosity has carried over into the general election before.

In 1980, the nomination fight between Jimmy Carter and Ted Kennedy lasted all the way to the convention. The result was a drop in the number of liberals who voted in the fall.

In 1992, Pat Buchanan staged a conservative challenge to George H.W. Bush that left many of his followers angry at the incumbent. The result was a drop in the number of conservatives who came out to vote in the general election.

Both Carter and Bush lost those elections.

The CNN/Opinion Research Corporation poll was conducted by telephone from Friday through Sunday, with 1,019 Americans questioned, including 227 registered Democrats who said they support Clinton and 218 registered Democrats who said they back Obama.